Many current aircraft use bleed air extracted from the main propulsion engines to supply conditioned air for various pneumatic systems throughout the aircraft. This includes commercial air transport aircraft, business jets, and military aircraft that are powered by turbo-jet, turbo-fan, and turbo-prop engines. The air extracted from the main engines is supplied to and controlled by a bleed air system, which extracts air from different ports of the compressor section of the turbine engine, and directs this air to various pneumatic loads via valves and ducting.
The valves in many bleed air systems are actuated by a fluid to move at least between a full-closed position and a full-open position. To do so, pressurized fluid may be routed to a fluid actuator in which a piston or a diaphragm is pressurized to move a valve element in the flow body of the valve. Recent engine designs have specified that one or more valves in the bleed air system also be moved to an intermediate position, between the full-closed and full-open positions. More specifically, that the intermediate position is the normal position of the valve, and that the valve is moved to the full-open position or the full-closed position in response to pneumatic actuation forces. The arrangement of an actuator to implement this functionality can be complex, and hence relatively expensive.
Hence, there is a need for a fluid actuated valve that can be moved from a normal, intermediate position to the full-open and full-closed positions using an actuator that is relatively non-complex, and thus relatively less expensive.